Pulse width modulation (PWM) is a known technique for DC voltage regulation, and is widely used in maintaining a constant output voltage despite wide variation in the input voltage and despite wide variations in load current. This technique is used to supply DC power to many different electronic systems.
In general, all pulse width modulators employ switching circuitry to generate pulses which are smoothed by an inductor-capacitor filter network to produce a substantially constant output of a DC voltage level. The magnitude of the DC output voltage is controlled by the duty cycle ratio of the switching circuitry.
To maintain a constant output voltage level, a feedback arrangement is conventionally employed. This calls for an output voltage to be compared with a stable voltage reference for developing an error signal by way of an error amplifier the output of which controls the duty cycle ratio of the switching circuitry by way of a comparator. When the output voltage drops too low, the error amplifier increases the switching duty cycle; when the output voltage rises too high, the switching duty cycle is reduced.
In addition, conventional buck regulated power supplies are inefficient due to losses in the switching circuitry and heat dissipation in the cores of the inductors. The heat dissipation is high due to the high operating frequency of the switching circuitry, which is typically greater than 250 KHz.
As will be explained, the present invention provides an efficient low power, buck regulator power supply that operates at a low switching frequency, minimizes gate drive power in the power converter, and maintains minimal dissipation in the control circuitry.